Notices of Memoirs — Brief Abstracts. 137 



These analyses may be usefully reproduced. 



Silica 51-08 



Titanic acid 1-24 



Alumina 16-38 



Ferric oxide 4-27 



Ferrous oxide ... 7-33 



Manganous oxide 0-31 



Magnesia 2-07 



Lime 8-12 



Soda 6-12 



Potash 3-63 



Phosphoric acid... 0-05 



Chlorine \ , 



Fluorine ] ^""^^^ 



Water 0-78 



II. 



III. 



IV. 



V. 



54-93 



... 55-74 



... 66-42 



.. 47-52 



0-28 







... 0-31 



.. 1-13 



19-36 



... 12-40 



... 13-07 



.. 17-35 



3-68 . 

 6-48 . 



•• } 13-16 



...} 366 



4-36 

 ■•• 3-05 



0-06 



.. 0-19 



trace 



.. 026 



2-16 



.. 5-92 



1-30 



.. 4-07 



6-27 . 



.. 7-28 



1-19 



.. 1-85 



3-14 . 



.. 3-88 



6-09 



.. 2-38 



0-73 . 



.. 0-60 



7-36 



.. 4-63 



004 , 



• • ••• 



• • •*• 





trace . 













2-16 



'.. 2-73 



6-73 



... 1290 



101-38 99-29 101-80 100-13 99-50 



I. Tachylyte; Bobenhausen ; by Mohl. Spec. grav. 2-686. 

 II. Tachylyte; Sababurg ; by Mobl. Spec. grav. 2-757. 



III. Tacliylyte ; Sasebuhl ; by Schnederman. Spec. grav. 2-578. 



IV. Tachylytic Glass (tachylytisches Glas) ; Rossberg ; by Petersen. 



Spec. grav. 2-524. 

 V. Hydrotacbylyte ; Eossberg ; by Petersen. Spec. grav. 2-130. 



P. W. R, 



IV. — Bkief Abstbacts for 1873. 



Tregay, Capt. William. Some Remarks on Crossbranches and 

 Crosslieads ; being an Inquiry into their Effect on Mineral 

 Lodes. Bep. Miners' Assoc. Cornwall and Devon for 1872-3, 

 pp. 57-61. 



By crossbranches are meant small local branches, sometimes only 

 extending the breadth of the lode they traverse. The details of 

 some of these are considered, and it is concluded that in many cases 

 they have a beneficial effect on the lodes, when they are filled with 

 carbonate of lime ; whilst when they are hollow or filled with quartz, 

 the lodes are less productive. 



Collins, J. H. (1). Note on the Rocks and Goonbarrow Mines, 

 near St. Austell. (2). Note on the Evidences of Vertical 

 Movement in the Lodes of Cornwall. (3). Note on the 

 Iron Deposits at Smallacombe, in Devonshire. Bep. Miners' 

 Assoc. Cornwall (ind Devon for 1872-3, pp. 66-71. 



(1). The mines are worked for tin and iron. There is a large 

 open work in a hill of granite (the felspar of which is in parts de- 

 composed, forming china-clay), crossed by tin-lodes. A plan and 

 section are given. The hard schorlaceous bands in the granite give 

 evidence of pseudomorphism on a large scale, and are more like 

 veins of segregation than true fissure veins. In the lodes crystals 

 of felspar have been replaced by quartz, schorl, and cassiterite. 



(2). A tin-lode at East Rocks Mine, near St. Austell, is inferred 



